LMMS

Linux MultiMedia Studio (LMMS) is a music creation tool that's similar to FL Studio (with which it's compatible), created to help you produce music from scratch through an intuitive yet comprehensive and full-featured interface, with support for MIDI keyboards and other specialized peripherals.

The first thing you'll notice about Linux MultiMedia Studio is all the windows you can keep open simultaneously, giving you access to all the music creation tools you need. The advantage of this is that, depending on what you're trying to make (a beat, a bassline, a simple melody...), you can keep only the windows you need.

The program includes different effects and sound keyboards that you can play around with when creating your music. These keyboards can be operated manually, as well as with a specialized MIDI keyboard, or you can import a file in OGG or WAV format to work with it from any of the interface's windows.

In addition to this, Linux MultiMedia Studio includes a 64-channel FX mixer that supports lots of different effects. You can load dozens of instruments and add hundreds of sounds from the mixer. Again, both manually or with the appropriate tools.

Linux MultiMedia Studio is an incredibly comprehensive music creation tool, and its only drawback, if there is one, is that it doesn't allow you to export your work in MP3 format. Instead, you can export it as a FLV, VST, or MIDI file.